U.S. Pat. No. 6,152,087 discloses a boiler tube shield having a cylindrical or semi-cylindrical shape and adapted to be attached around an outer peripheral face of a boiler tube with mortar. The boiler tube shield includes a plurality of ceramic bodies closely arranged along their parting planes, wherein the parting planes includes a restraining portion for restraining slippage of each of the ceramic bodies.
U.S. Pat. No. 6,136,117 disclose a method of attaching a boiler tube shields having a cylindrical or semi-cylindrical shape around an outer peripheral face of a boiler tube with mortar. The boiler tube shields, are a plurality of ceramic bodies closely arranged along their parting planes, wherein the parting planes includes means for restraining slippage of each of the ceramic bodies along the parting planes.
The tube shields in U.S. Pat. Nos. 6,152,087 and 6,136,117 requires that tube shield halves are pushed together axially into the locking position, whereby it is impossible to apply this kind of tube shield on a tube bend. During application of the tube shield must halves be pressed towards the original tubes against the resistance of the mortar while pushing at least one of the halves axially. This makes assembly cumbersome. The design will also make it difficult to replace individual tube shield halves if more than one set of tube shield halves are mounted on the original tubes, as the individual tube shield half to be replaced needs to be pushed axially over the tube against the tube shield halves already mounted.
An object of the invention is to provide a boiler tube shield and a method for attaching such a tube shield to a boiler tube, which can assuredly protect the boiler tube from corrosion or erosion or a combination of both corrosion and erosion.
A further object with the invention is to provide a tube shield which has a better means for restraining slippage of the tub shield parts, compared to the two US documents above.
Yet another object with the invention is to provide a method for assembling the inventive tube shield and enabling replacement of individual tube shield halves.
A further object is to enable a tube shield system enabling the same solution also for tubes bends having a curvature.
Still another object is to enable a tube shield protecting system being less cumbersome to install, requiring a simple assembly procedure, where halves are simply only pressed over the original tubes to be protected, and where the refractory cement is pressed out into the gaps between halves and after curing establish the necessary locking function for the halves.
The tube shield according to the claimed invention has a cylindrical or semi-cylindrical shape and is, adapted to be attached around an outer peripheral face of a boiler tube with refractory cement. The boiler tube shield comprising at least two shield parts closely arranged along their parting planes, positioned on a part of the original boiler tubes, and wherein the parting planes of the shield parts comprise means for locking each of the shield parts along the parting planes. The tube shield is divided into two halves, and their parting planes extend substantially axially. The locking means includes a dovetail engagement. The parting planes of the shield parts may be inclined or parallel to a flat plane containing a central axis of the cylindrical or semi-cylindrical boiler tube shield, when assembled around the boiler tube in the form of the shield. The parting plane of each shield part at each of both sides thereof may comprise a dovetail portion for locking each shield part along the parting plane. In the boiler tube shield, the dovetail portion preferably forms a locking with respect to the parting plane of each shield part that movement of the shield part in a direction orthogonal to said parting plane may be restrained.
These and other objects, features and advantages of the invention will be easily appreciated upon the reading of the following description of the invention when taken in conjunction with the attached drawings, with the understanding that some modifications, variations and changes of the same could be easily made.